messagedatabase.java

本平台是以web2.0为基本的标准

package com.afuer.chat;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Reader;
import java.util.Iterator;
import java.util.LinkedList;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.thoughtworks.xstream.io.xml.JDomDriver;
import com.thoughtworks.xstream.XStream;

/**
 * To store the message.
 */
public class MessageDatabase {
    private static Log log = LogFactory.getLog(MessageDatabase.class);

    private static final int VERSION = 2;

    private int version = VERSION;
    private String persistFile;
    private LinkedList messages;
    private LinkedList stickyMessages;

    public LinkedList getMessages() {
        return messages;
    }

    public void setMessages(LinkedList messages) {
        this.messages = messages;
    }

    public LinkedList getStickyMessages() {
        return stickyMessages;
    }

    public void setStickyMessages(LinkedList stickyMessages) {
        this.stickyMessages = stickyMessages;
    }

    public int getVersion() {
        return version;
    }

    public void setVersion(int version) {
        this.version = version;
    }

    private void upgrade() {
        if (messages != null) {
            for (Iterator it = messages.iterator(); it.hasNext();) {
                Message msg = (Message) it.next();
                msg.upgrade(version);
            }
        }
        if (stickyMessages != null) {
            for (Iterator it = stickyMessages.iterator(); it.hasNext();) {
                Message msg = (Message) it.next();
                msg.upgrade(version);
            }
        }

        // force the version
        version = VERSION;
    }

    static MessageDatabase load(String persistFile) {
        MessageDatabase messageDatabase = null;
        Reader reader = null;

        try {
            reader = new FileReader(persistFile);
            XStream xstream = new XStream(new JDomDriver());
            messageDatabase = (MessageDatabase) xstream.fromXML(reader);

            // for upgrade
            if (messageDatabase != null) {
                messageDatabase.upgrade();
            }
        }
        catch (FileNotFoundException ex) {
            ;
        }
        finally {
            if (reader != null) {
                try {
                    reader.close();
                }
                catch (IOException ex) {
                    log.warn("Exception when closing reader", ex);
                }
            }
        }

        if (messageDatabase == null) {
            messageDatabase = new MessageDatabase();
            messageDatabase.setMessages(new LinkedList());
            messageDatabase.setStickyMessages(new LinkedList());
        }

        messageDatabase.persistFile = persistFile;

        return messageDatabase;
    }
    void persist() {
        FileWriter writer = null;
        try {
            writer = new FileWriter(persistFile);
            XStream xstream = new XStream();
            xstream.toXML(this, writer);
        }
        catch (IOException ex) {
            log.warn("fail to persist " + persistFile, ex);
        }
        finally {
            if (writer != null) {
                try {
                    writer.close();
                }
                catch (IOException ex) {
                    log.warn("Exception when closing writer", ex);
                }
            }
        }
    }
}